A thermal collector of solar energy collects energy of solar radiation that is incident upon the collector. Collected energy is transferred as heat to a heat using apparatus such as power generation equipment, a home heating or air conditioning system, a heat pump, or the like.
Electric power plants typically include heat generating equipment, equipment to transfer generated heat to a motive fluid and a turbine-generator driven by the motive fluid. In conventional power plants heat is generated by a nuclear reactor, or by combustion of a fossil fuel such as coal, oil, or natural gas. In one type of solar electric power plant solar energy is collected as heat which is transferred to the motive fluid. Such a solar electric power plant is an attractive alternative to those power plants that depend upon combustion of fossil fuels, especially in view of the generally rising costs of fossil fuels.
Typically a large number of thermal collectors, covering a substantial area upon which solar radiation is incident, is required to collect sufficient heat for generation of electric power in a solar power plant as above described. A thermal collector for use in such a solar power plant desirably operates at high temperatures which permit efficient conversion of the collected energy to electrical energy. Such a collector further desirably collects solar energy at an elevated efficiency at such operating temperatures, for then the required number of thermal collectors is reduced.
A thermal collector of solar energy typically includes an absorber to absorb energy of solar radiation and transfer such energy as heat to a heat transfer medium. In a class of proposed absorbers, an absorber comprises multiple layers of materials, each layer having certain optical properties such that the combined optical effect of the layers is that of an absorber. Usually the thickness of each layer must be carefully controlled, and the layers must be deposited on a carefully prepared substrate. In some multilayer absorbers, destructive reactions may occur between the materials of the various layers, or temperature changes may vary the optical properties of a layer, thereby reducing the overall effectiveness of the absorber. Other multilayer absorbers are effective within a limited band of wavelengths of the solar radiation. Some multilayer absorbers are most effective when the angle of incidence of the solar radiation is within a limited range.
There appears to be a need for a thermal collector of solar energy that is capable of efficient collection at operating temperatures that are suitable for efficient conversion of collected energy to ellectricity, especially when heat exchange and rotational apparatus participate in such conversion. Such a collector advantageously is effective at widely varying wavelengths and incidence angles of solar radiation, and retains its desirable properties at elevated temperatures.
The description of prior art herein is made on good faith and no representation is made that any prior art considered is the best pertaining prior art, nor that the interpretation placed on it is unrebuttable.